The present invention relates to the modification of organic polymer surfaces and the articles produced therefrom. Particularly, the invention relates to organic polymers having a surface modified to improve the adhesive characteristics of such polymers.
It is well known in the art to surface treat organic polymers such as polyesters to improve the utility of such polymers. For example, it is known to treat polyester fibers to improve the adhesion of the polyester to substances such as rubber in the manufacture of tires. In U.S. Pat. No. 4,054,634, multifilament polyethylene terephthalate yarn is treated with a two-part finish, one part of which is applied after spinning and one part of which is applied after drawing. The first part contains a defined polyoxyethylated-polyoxypropylated monoether whereas the second part contains the monoether in combination with a defined epoxy ether silane and a sufficient amount of a water soluble alkaline catalyst to raise the pH to 8-10. Also see U.S. Pat. No. 4,348,517 wherein the same epoxy ether silane is combined with the triglycidyl ether of a glycerol and a defined diglycidyl ether and is used as a fiber finish for polyester yarn.
U.S. Pat. No. 3,793,425 also describes a process for improving the adhesion of polyester material to rubber. In the process, undrawn polyester yarn is coated with a composition containing an epoxy resin which is preferably buffered with an alkaline agent, such as sodium carbonate, lithium carbonate, potassium carbonate or ammonium hydroxide. The use of epoxy resins with alkaline catalysts to improve the adhesion of polyester to rubber is further disclosed in U.S. Pat. Nos. 3,423,230 and 3,464,878.
A process for treating chemically stabilized polyester material to improve the adhesion of the polyester to rubber is also described in U.S. Pat. No. 4,751,143. As noted therein, the aging period for chemically stabilized, adhesive activated polyester material can be reduced by contacting the material before it is substantially drawn or stretched with a composition containing a defined epoxide compound catalyzed with ions of at least one of potassium, cesium, or rubidium at a pH of between about 7.5 to about 13.0.
The application of finishes to the polymer surface generally produces a temporary surface condition such as lubrication or electrostatic charge dissipation which may be removed when the surface is subsequently exposed to multiple processing steps. Additionally, polyester surface modifications of the prior art employing epoxies to improve the adhesion of polyester to rubber for example, have resulted in the creation of toxic working conditions in the manufacture of such surface-modified polyester or in the production of articles which in subsequent processing or use would expose individuals to toxic conditions.
Other approaches employed in the art to adjust the characteristics or properties of organic polymer surfaces include electrolytic and plasma treatments. However, these processes are costly and have limited processing rates. The application of a strong acid or base has not been particularly effective in modifying surfaces and can penetrate beyond the surface, particularly in fiber structures, to cause strength loss.
Polyisocyanates have been employed to enhance adhesion in the manufacture of polyester yarns (see U.S. Pat. No. 3,549,740). These materials have been applied at relatively high concentration levels (greater than 0.5 weight percent) and so generate obnoxious vapors, produce deposits on process rolls and bond filaments to filaments in the yarn bundle. Similar processing problems are encountered in the application of known polyester adhesives such as those based upon resorcinol-formaldehyde resins described in U.S. Pat. Nos. 3,660,202 and 3,318,750.
Molecular chains of aromatic groups connected by methylene groups attached to carbon atoms in the benzene rings have been employed to enhance adhesion of polyester articles (see British Patent Specifications 1,140,528 and 1,156,624). These products have been used as an RFL additive for adhesions and not as individual components. However, it has been found that for such products to be effective, 1.5% of the weight of the yarn is required. At this level, the yarns bond together making the processing very difficult.
Accordingly, it would be desirable to have the capability to permanently modify the organic polymer surface employing a non-toxic process and improve the processing of the organic polymer in the production of articles of manufacture.